Thermostatic electric-circuit controller



A. E. CHISHOLM THERMOSTATIC ELECTRIC CIRCUIT CONTROLLER 2 Shays- Sheet 1 Filed April 13 1920 Oct. 4, 1924.

A. E. CHISHOLMQ THERMOSTATIC ELECTRKC CIRCUIT CONTRQLDER Sheets-Sheet '2 Filed April 13, 1920 m, 2 42244, sq

' 1 Be it known that I, ALLEN E. Cmsn'omg provement in Patented 0a. 14, 1924.

UNITED, STATES" ALLEN E. CHISHOLM, 0F PORTLAND, OREGON THERMOSTATIC ELECTRIC-CIRCUIT CONTROLLER.

Application filed April'm i920. Serial No. 573,557.

T 0'-all it may comm:

a citizen of the United States, and a resident of Portland, county of Multnomah, State of Oregon, have invented a new and usefulIm- Thermostatic Electric-Circuit Controllers, of which the following is a specification. I A

My invention relates to means for eifecting' the thermostatic Control of an electric circuit so as to make or break such circuit in the presence of a predetermined temperature.

The purpose of my invention briefly stated is this: The movement of a thermostatic element per degree of change in temperature is only slight, and if suchimovement alone I j be depended on for causing the break on make in an electric circui serious consequences may ensue, In snort, there 1s a critical period-just at he instant of making or breaking the circ lii and if the'action of the means effecting suc'h nakeor break be not rapid enough, there is a tendency of causing an are between the electrical contacts during the operation of the make-andbreak. p

With .circuits of low voltage and small amperage, such arcing may be but sli ht, nevertheless it will eventually so mug en the contacts that they become unreliable for further service; and in circuits of greater amperage and moderate volta e, the. arcing may be so severe as to cause t e contacts to be melted or welded together.

Hence, a thermostatic control for a make or break in which oneconta'ct of the circuit is carried by a thermostatically positioned .member and depends on tliemotion ofsaid latter member for making or breaking the circuit will not answer the purpose as above outlined.

The object of m invention is to provide thermostatically operated means instantaneously as to prevent the forming of an are between said electrical contacts.

attain my objectin the combination with,

ithe make-and-break of an electric circuit, of

' trolled-whereby sai mechanical means referablylspring' con- 3 make-and break is operated with great ra idity, and thermostatic means by which sai m chanical means are thrown into action. w I

I will describe the practical use of my invention inconnection with an electrically wluch will effect the make on break of the circuit so fir in a fire alarm system: It is well heated sad-iron, also with regard to anlauto- .matic electric fire alarm.

the excessive heat of the iron is dissipatedby the damp clothes; but when the iron is permitted to stand with the current on, its

temperature Will rise rapidly to the dangerous point; and if the iron rests on an inflammable surface it may ignite the latter; or even if such be not the case, the excessive heat will tend to damage, or probably destroy the heating element of the ironi The object of any automatic thermostatic control for electric'iron's is of course to break the circuit before the danger point is reached; but for such controlling means to be malntained in a dependable state the devices must be adapted to effect the interruption of the circuit-instantly, in the presence of the predetermined maximum degree of heat.

Furthermore, in anelectric iron, two essential features are required to insure safety.

First: The devices must be so arranged that when once the circuit is interrupted by the presence of the predetermined excessive degree of heat, the electric circuit will not become automatically re-established, with the mere drop in temperature below the predetermined maximum degree; but, to the contrary, the devices must be so arranged that some manual action on the part of the operator is required for re-establishing the circuit; for, if the devices are so arranged as tocause the automatic re-establishment of the circuit upon a mere drop in temperature, then the iron would be maintained at a temperature close to the danger point, and if forgotten and neglected, a re may result.

Secondly: The device should be so arranged that when once the current is interruptedbecause of an excessive degree of heat having been attained by the iron, the circuit cannot be re-established by any manual adjustment of the devices until the temperature has again fallen below the predetermined maximum degree of heat; otherwise,-the

ctically nullified.

Describing next the use of m invention own that on lines that are normally open and which ction of the automatic-cdntrol would be be gradually diminished, as with the aver- .age thermostatic -controlling device, then a condition may arise whereby; the static discharge will start an are which will be maintained .by the normal'line voltage.

Furthermore, even if an arc is not main tained, thestaticdischarges will eventually roughen the contact points; therefore, as

' obvious it is necessary that the make and break should be instantaneous i'n its oper-. ations. In Sheet "1 of the accompanying drawings, I have shown 'my device as used in connection with an electric sad iron, namely, Fig. 1 is a plan view of an electrically heated iron embodying my invention, the cover or housing and handle of the iron ,being removed;

ig. 2 is a transverse section of Fig. 1,

on the line 2-2;

Fig, .3is a front elevation of the interior devices of the iron, the housing or cover and the handle being shown in section;

Fig. 4' is a perspective view of the device combined in m invention with arts broken away to disc ose parts which otherwise would be covered; y V

Fig. 5'is a" perspective inverted sectional detail ofthe adjustable latch hooks includi ed'in my in ventiong In Figs. 6 to 9 inclusive I have illustrated the practical application of my invention to an electric fire-alarm system; thus, Fig. 6 is an elevation of an electrical alarm device embodying my invention, the electric circuit being indicated by diagram;

Fig. 7 is a plan view as seen with the housing 2 removed from its support;

Fig. 8 is a transverse section on the line 8-8 of Fig. 7; and

Fig. 9 is a perspective view of certain arts of the mechanism embodying my inyention.

The general construction and operation of my device as shown in Figs. 1 to 5 in-' elusive illustrating, as mentioned the use of my invention in an electrically heated sad iron are as follows: a

' a and a are complementary members of the thermostat element which comprises two members a a each' com osed of two-stri s s P P of metal, for example, of unequal co-efiicients of expansion. The strips of which each of said members -a, a is composed are initially curved to the form shown, and are then rigidly fastened together, preferably by riveting. 'The thermostat members a, a are then combined in the form of a full elliptic spring, the extremities of said members being hinged together as at (1*.

By providing a thermostat element constructed as shown, that is to say, in theform of a full elliptic spring comprising two members as a, and a, an appreciably greater movement is obtained than if a thermostatic element were employed comprising only one memberlike a or a.

The thermostatpmember a is firmly mounted in slots provided in supporting posts 0 between insulating mica plates'b; the posts o being aflixed on the base plated.

l'n the design shown in Figs. 1 to 5 inclusive, the metal of the least co-efiicient of expansion, is placed on the outer or longest. side of the curved thermostatic members. Hence, under the action of heat, the greater coeflicient of expansion of the meta com} prising the inner leaves of the thermostat members a and a will tend to flatten the ellipse, and thus shorten the transverse axis which gives the mechanical movement desired.

A latchbar 6 provided with hinge ears at one end is hingedto a hinge plate 9 by a hinge-pin f,' the hinge member g being riveted to the thermostat member a.

The opposite end of the latch-bar c has a perpendicular portion e, which carries an adjustablel'atch-hook Is, the latter being fastened to said latch bar by an adjusting screw 7', as more clearly shown in Figs. 2 and 5. 'An insulated button s,.on the latch bar e, projects up thru a hole in the cover. 3. The button- 8 is secured to the hook is by-a screw' 8', and thelatter bears in a slot 8 I A spring h is riveted to the hinge-plate g, and the free end of this spring bears under tensidn, against the underside of said latch bar, normally lifting the latter :and thus breaking or opening the circuit as will be seen.

' n is a metallic plate contact-member, fixed in place on the base plate d between insulating mica plates p by a screw 0, which threads into the ase plate (I. 1

l is a brass spring riveted at its fixed end to the latch bar e, and provided at its free end with a non-corrosive tip m.

The latter'constitutes one of the-electrical contacts of the make-and-break of my device, and the plate n has a stepped portion 12. which constitutes the other electrical contact member.

A; latch hook i is rigidly fastened on the thermostat member a and the parts are .so arranged that in temperatures under a predetermined maximum degree the lat'chhook a i will be in en agement with the latch-hook k of the latchar e.

w is an arm constituting an electrical connection of the heating element of thesad iron with the thermostat member a, to which one end of said arm w is fastened by-a stud'screw r. a

a: is a bar constituting an electrical connection between the source of electric energy and the electrical contact member n to whichit is fastened by stud-screw g.

y is an electrical connection between the heating element of the iron, and the source of electric energy thru a member a.

t, t are two studs firmly supported'on to bar a, thence 'thr u plate n to contact m,

thence thru spring contact finger l toilatchbar e, thence thru hingb-ear g, to thermostat member a, thence thru stud r, to arpi w, thence to heating element, thru the latter to arm 3 and thence back to service line.

Contact is maintained between the contact members in and n, thru the medium of the latch-bar e, which is held in the osition shown against the tension of spring ii, by restraining devices, that is to say, thru-the engagement of latch-hook k,- car ried by the latch bar e, withlatch-hook Under normal heat conditions, the thermostatic action will be, insufficient to cause the parts to function so as to open the'circuit. As soon, however, ,as the temperature exceeds the predetermined degree, the move ment of the thermostat element will be such as to cause the latch hook i, to disengage from latch hook it of the latch-bar ea instantly throw the latch lever e up thereby instantly separating the contacts m. and

n, and breaking the electric circuit.

After this action has taken place, the elec. tric circuit cannot be re-established and maintained until the temperature has dropped to such extent as to re-adjust thethermostat so that latch hook is may again.

4 be engaged withthelatch hook When sufiicient cooling has'taken place,

the insulated button a maybe pressed down The tension of the spring It will then- It will be remembered that no means are provided on the device for changing the normal electric current as normally passing thru the device. Hence the operation of the thermostatic means to effect a break in. the circuit is due to arise in temperature above a predetermined degree resulting from the heat acquired by the device while being supplied by'the normal current in a normal way. It the work done with the iron disipates the heat radiated by the-latter to such extent as to keep this heat belowa predetermined temperature, nothing will' happen; but ifthe degree of heat acquired by the iron runs above" said temperature the latch holding the make-and-break in its circuit making-position will be released, and the latch cannot then again be readjusted to its holding positions until the temperature is reduced.

Therefore, the statement in some of the claims, that the thermostatic means are adapted to render said latch holding means inoperative by the passing-therethru of the normal electric current thru the normal cir,

cuit. It is to be understood that there is to be noma'nual change or adjustment effected -in the operation of the device, so as to alter the relationship of thecurrent passed thru the device and resistance element carried by the latter.

Referring now to 6 m9 inclusive, I have. shown mythermostat as applied to a fire-alarm system. Inthis application, the

. parts shown which correspond with similar The pins 0, c extend thru theframe d, and I are provided with nuts 8' and lock nuts t. The cover 2 is held in place by the lock nuts 't', and a seal t prevents unauthorized removal of the cover. I 1

A lint o' engages the'stud o, and the contact tip member m; is omitted. It is to be noted that the base-plate d is extended. so as to permit the thermostat to be conveniently fastened. to the ceiling, and the electrical connections 3 and 4 connect directlywith the studs 9 and r respectively. y Batteries 5, 6 rovide'a sourceof current for energizing t e circuit. 7 is an alarm gong,- 8 is a solenoid switch, and-9 is a drop alnmnciator which indicates the location of t 0 re. Y

release the engagement between latch'hook i, and latch hook k. The spring h? willthen rock the lever 0 so as to cause the member 8 to make electrical contact with the member I The 'circuit ivill thus be closed and all as follows: I

' Energizing of the solenoid switch will parts contained in the'circuit will function close the circuit of the gong 7, causing to operate and thus give the alarm. j

Simultaneously, the annuncia'tor will function so as to drop the indicator and thus point out the location of the fire. A

' acterize my invention.

I claim: I I 1. In an electric circuit provided with a 'inake-and-break element, the combination with the latter of a thermostatic element comprising two members arranged like a circuit, and devices for holding said movfull elliptic spring, one of saidmembers being fixed in place, a movable member carried by said fixed member of said thermostatic element, one contact in said make and break carried by said movable member, the other contactof said make and break being relatively fixed in, plaee, spring actuated means for throwing said movable member. into its position for opening the circuit, and devices foigholding said movable member in its position forfclosing said circuit, said thermostatic element being adapted'at a given temperature to release said movable member from saiddevices.

- 2. In an electric circuit provided with a make-and-break element, the combination with the latter of a thermostatio -element, comprising two members arranged like a full elliptiespring, one of saidginenrbers being fixed in place, a movable mei'nb'r carried by said fixed member of said thenmostatic element, one contact in said make and break actuated by said movable member, the other contact-of said make and break being relatively fixed in place, spring actuated means for throwing said movable member into its position for opening the able member in its position for closing said circuit, said thermostatic element being adapted at a given temperature to release said movable member from said devices.

"being fixed in,place, 'a movable membencarried by one memberof said thermostatic element, one contact of said make and break being actuated by said movable member, the other contact of said make and break being relatively fixed -in place, spring ac- "tuated means for throwing said movable member into one-position 'relative'to the closing of the circuit, and devices for holding said movable member in'position for closin the circuit, said thermostatic 'ele ment eingfadapted to release said member at a given temperatgre, thereby closing the circuit.

4. The combination of an electric circu it provided with a make-and-break ele mht, a thermostatic element comprising two-.members arranged'like a full elliptic spring one of said membersbeing fixed in place, amovable piece carried by one member of said thermostatic element, one contact in said make and break-carried 'by,-said movable piece, the other contact of said make and break being relatively fixed inplace, automatic fneans for throwing said movable piece into.its position foropening said circuit, and devices for holding said movable piece in its position for closing said circuit, "said thermostatic element being adapted at a given abnormal temperature to release said movable member from said -,holding devices and thereby rendering'the latter inoperative during the continuance.

of said abnormal temperature. I

5. The combination of an electric circuit provided with a make-and-break element,'a thermostatic element comprising two members arranged like a full elliptic spring-one Cofsaid members' being fixed in place, a

movable piece carried by one member-of said thermostatic element, one contact in said make and break carried by said movable. iece, the other contact of said make and reak being relatively fixed in place,

spring actuated means for throwing said 'movable piece into its position .for openmg said circuit, and devices for holding said moLvable piece in its position for 010s: ing said circu t, said thermostatic element be ng ada ted at a given abnormal temperature to re ease said movable membcr from 3. In an electric circuit provided-with a" said holding devices and thereby rendering make-and-break element, the combination with the latter of a thermostatic-elementcomprising two members arranged like a, full elliptic spring, one of said members the latter inoperative during the continw ance of said abnormal temperature.

ALLEN E. CHISHOLM. 

